From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4DE7180C for ; Tue, 27 Sep 2022 13:16:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 378D0C433D7; Tue, 27 Sep 2022 13:16:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664284576; bh=EHb6HHsgIXEzrlOmrEyvqnUYIwHi5+s9QYRqtpeUv3o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rrQDbsHeOnO2szQNPiDbgjuGFtIn92QYZX5NGxABo43qZbBSRU5ndZKpvqCnS1/Ai zbQWDgziSbm1uS3Y+vF0SOO3c0VrCJ7fSq1ukwPBeQjUizBgoMLIQGmLCzdMpabroJ LLTsZXqDcO36IVzTPv15BJOISjNNJSgzRi5k4ep5Lk98KE3yGl2A270dG/BlaaX3Ha J8zW7c4kKrkW+WuMM0/XrOqC92V/y1IPYkafbIXNSNUuwfaPQkjZKmH1t1YCB1+DDb +ozOsPioZ1J0Nfq9ayTT2G4al0WTz47uFQN/7z37l0G+mRgrsYuTy29RH/qxc+FbRF KZIWRGzpw3/8w== From: Miguel Ojeda To: Linus Torvalds , Greg Kroah-Hartman Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, patches@lists.linux.dev, Jarkko Sakkinen , Miguel Ojeda , Alex Gaynor , Geoffrey Thomas , Wedson Almeida Filho , Sven Van Asbroeck , Gary Guo , Boqun Feng , Maciej Falkowski , Wei Liu , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= Subject: [PATCH v10 06/27] rust: add C helpers Date: Tue, 27 Sep 2022 15:14:37 +0200 Message-Id: <20220927131518.30000-7-ojeda@kernel.org> In-Reply-To: <20220927131518.30000-1-ojeda@kernel.org> References: <20220927131518.30000-1-ojeda@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Introduces the source file that will contain forwarders to C macros and inlined functions. Initially this only contains a single helper, but will gain more as more functionality is added to the `kernel` crate in the future. Co-developed-by: Alex Gaynor Signed-off-by: Alex Gaynor Co-developed-by: Geoffrey Thomas Signed-off-by: Geoffrey Thomas Co-developed-by: Wedson Almeida Filho Signed-off-by: Wedson Almeida Filho Co-developed-by: Sven Van Asbroeck Signed-off-by: Sven Van Asbroeck Co-developed-by: Gary Guo Signed-off-by: Gary Guo Co-developed-by: Boqun Feng Signed-off-by: Boqun Feng Co-developed-by: Maciej Falkowski Signed-off-by: Maciej Falkowski Co-developed-by: Wei Liu Signed-off-by: Wei Liu Signed-off-by: Miguel Ojeda --- rust/helpers.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) create mode 100644 rust/helpers.c diff --git a/rust/helpers.c b/rust/helpers.c new file mode 100644 index 000000000000..b4f15eee2ffd --- /dev/null +++ b/rust/helpers.c @@ -0,0 +1,51 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Non-trivial C macros cannot be used in Rust. Similarly, inlined C functions + * cannot be called either. This file explicitly creates functions ("helpers") + * that wrap those so that they can be called from Rust. + * + * Even though Rust kernel modules should never use directly the bindings, some + * of these helpers need to be exported because Rust generics and inlined + * functions may not get their code generated in the crate where they are + * defined. Other helpers, called from non-inline functions, may not be + * exported, in principle. However, in general, the Rust compiler does not + * guarantee codegen will be performed for a non-inline function either. + * Therefore, this file exports all the helpers. In the future, this may be + * revisited to reduce the number of exports after the compiler is informed + * about the places codegen is required. + * + * All symbols are exported as GPL-only to guarantee no GPL-only feature is + * accidentally exposed. + */ + +#include +#include + +__noreturn void rust_helper_BUG(void) +{ + BUG(); +} +EXPORT_SYMBOL_GPL(rust_helper_BUG); + +/* + * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type + * as the Rust `usize` type, so we can use it in contexts where Rust + * expects a `usize` like slice (array) indices. `usize` is defined to be + * the same as C's `uintptr_t` type (can hold any pointer) but not + * necessarily the same as `size_t` (can hold the size of any single + * object). Most modern platforms use the same concrete integer type for + * both of them, but in case we find ourselves on a platform where + * that's not true, fail early instead of risking ABI or + * integer-overflow issues. + * + * If your platform fails this assertion, it means that you are in + * danger of integer-overflow bugs (even if you attempt to remove + * `--size_t-is-usize`). It may be easiest to change the kernel ABI on + * your platform such that `size_t` matches `uintptr_t` (i.e., to increase + * `size_t`, because `uintptr_t` has to be at least as big as `size_t`). + */ +static_assert( + sizeof(size_t) == sizeof(uintptr_t) && + __alignof__(size_t) == __alignof__(uintptr_t), + "Rust code expects C `size_t` to match Rust `usize`" +); -- 2.37.3